Follow the rules to get the most clean air from HEPA filters

Bushfires, thunderstorm asthma and of course Covid-19 have made it imperative to get the best air filtration.

HEPA filters must placed in right spot and be large enough to be effective for the whole space.

In these past couple of years we have had air quality on our minds more than ever, starting with the Black Summer bushfires of 2019-20 and then transitioning into a pandemic of an airborne virus.

Short of modifying buildings and building codes to improve ventilation, it can be difficult to know what to do. Air purifiers can be part of the solution, says Sotiris Vardoulakis, professor of global environmental health at the Australian National University Research School of Population Health.

“There’s strong evidence that air purifiers can provide significant improvements to indoor air quality in relation to fine particles in particular and also, depending on the other features of the air purifier, other gases, volatile organic compounds etc,” Professor Vardoulakis says.

“But the most important improvement in air quality is related to fine particles, and we know that the smaller the particle, the deeper they go into our respiratory system. They can cause inflammation and they can translocate into the bloodstream. So, we want to get rid of these.”

Generally in Australia those particles derive from traffic, gas stove tops, wood-burning fires, and heavy metals. “In the past, we thought that these fine particles – PM2.5 – mainly affected respiratory cardiovascular health. Now there is increasing evidence that they can also affect brain health and cognitive function.”

Just having an air purifier in the room isn’t enough, he says. It must be of high quality, with a HEPA filter, placed at the right spot in the space according to the model’s instructions, and be large enough to be effective for the whole space.

“We sometimes see relatively small units in large spaces like lecture theatres or waiting rooms in hospitals or school, and obviously it’s not sufficient to have a single, very small air purifier to cover a very large space.”

The good news is that Australia’s air quality is generally pretty good compared with that of many other places – barring bushfires and thunderstorm asthma; the bad news is that there is no safe level of air pollution.

Smoke is only one air hazard.

“Even at low levels of air pollution there are some benefits from cleaning the air, especially for people who have pre-existing illnesses like asthma, chronic obstructive pulmonary disease, or other respiratory cardiovascular disease.”

Air pollution causes 2600 Australian deaths each year due, with seven million worldwide, according to the World Health Organisation. A WHO report in 2017 found that “the costs of air pollution to society have been put on par with smoking and obesity”.

“We’re not talking about people just dropping dead in the street from air pollution, but its impact on mortality calculated using ecological evidence and statistical techniques,” Professor Vardoulakis says.

“Everyone’s life is shortened a little bit because of exposure to air pollution. If we take all this shortening of life into account, then we can estimate the equivalent number of deaths related to air pollution.”

In 1849 a doctor called John Snow worked out that the cholera outbreak in London was being spread by contaminated water, and his discoveries led to a revolution in sewage and water treatment practices.

Air quality experts, like Professor Vardoulakis, believe we should apply similar lessons from the Covid-19 pandemic to air quality and ventilation regulations.

“By now most public health experts agree that Covid-19 is an airborne virus, and [what is required is] good ventilation and good indoor air quality.

“Air purification can be fitted into the infrastructure with filters that conform to embedded ventilation systems as well as portable air purifiers. We have seen these kinds of intervention being implemented in schools particularly in Australia, and healthcare settings.

“For many years the focus around air pollution was outdoors, because that is quite regulated. Few people thought indoor air quality was an issue, but now these kinds of attitudes are changing with increased awareness of indoor air quality’s effect on health and airborne infectious diseases.”

Aside from air purification, Professor Vardoulakis recommends reducing indoor air pollution by opening windows in good weather, not using a wood burning fireplace or a gas cooktop and removing sources of smoke such as cigarettes and candles.